Multi-range traversability indices for terrain-based navigation

Presents novel measures of terrain traversability at three different ranges, namely local, regional and global traversability indices. The local traversability index is related, by a set of linguistic rules, to local obstacles and surface softness within a local perception range, measured by on-board sensors mounted on a robot. The rule-based regional traversability index is computed from the terrain roughness and slope that are expected from video images of the terrain within a regional perception range obtained by on-board cameras. The global traversability index is obtained from a terrain topographic map, and is based on natural or man-made surface features, such as mountains and craters, within the global perception range. Each traversability index is represented by four fuzzy sets with linguistic labels {poor, low, moderate, high}, corresponding to surfaces that are unsafe, moderately unsafe, moderately safe or safe for traversal, respectively. These indices are used to develop a behavior-based navigation strategy for a mobile robot traversing a challenging terrain. The traversability indices form a basis of three navigation behaviors, namely local, regional and global traversal behaviors. These behaviors are integrated with a goal-seeking behavior to ensure that the mobile robot reaches the goal safely while avoiding obstacles and impassable terrain segments. The paper concludes with an illustrative graphical simulation study.